4 
Scientific Proceedings (40). 
2 (527) 
An inquiry into the nature of the changes in non-regenerating 
animals. 
By A. J. GOLDFARB. 
[From the College of the City of New York.] 
It was shown in a recent publication, 1 that very diverse groups 
of animals, that ordinarily regenerate such organs as the head, 
tail, leg, etc., could not be prevented from so doing by destruction 
of that part of the nervous system supplying the amputated 
region and adjoining parts. And vice versa, that the lack of 
regeneration was not due to the absence of stimuli passing through 
the central nervous system. 
The present studies pertain to the adult frog, selected as an 
example of an animal heretofore not known to replace a missing 
organ, such as the leg. A large series of sections of the amputated 
region of the leg, prepared at intervals of several days to over 
nine months, were studied and compared with similar sections 
of the leg of the newt, which regenerates its limb quite readily. 
Perhaps the most striking observation centers about the changes 
of the bone. In brief the evidence supports the view that that 
which retards or prevents the growth of the bony tissues cor- 
respondingly retards or prevents the growth of the adjoining 
tissues. It was found that while ordinarily no regeneration 
occurs, yet each of the tissues could, under appropriate conditions, 
replace the parts originally removed. 
These conditions are twofold. In the first place, regeneration 
of the limb seems to be dependent upon the development of the 
bony tissues. Ordinarily the exceedingly large growth of peri- 
osteum and cartilage is succeeded by regressive changes resulting 
in a "callous" like structure. When this occurs all further growth 
changes in other tissues thereupon cease. In one particular in- 
stance, the periosteum grew so rapidly that the "anlage" of the 
leg and foot were distinctly differentiated before the degressive 
changes set in. 
*A. J. Goldfarb, The Influence of the Nervous System in Regeneration, Journal 
Exp. Zool., vii, 1909. 
